Jackson is "the Java JSON library" or "the best JSON parser for Java". Or simply as "JSON for Java".

Jackson Databind Source Code files are provided in the source packge (jackson-databind-2.14.0-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Databind Source Code below:

⏎ com/fasterxml/jackson/databind/util/BeanUtil.java

package com.fasterxml.jackson.databind.util;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.introspect.AnnotatedMethod;

/**
 * Helper class that contains functionality needed by both serialization
 * and deserialization side.
 */
public class BeanUtil
{
    /*
    /**********************************************************
    /* Property name mangling methods: deprecated
    /**********************************************************
     */

    /**
     * @since 2.5
     *
     * @deprecated Since 2.12 replaced with {@link com.fasterxml.jackson.databind.introspect.AccessorNamingStrategy}
     */
    @Deprecated
    public static String okNameForGetter(AnnotatedMethod am, boolean stdNaming) {
        String name = am.getName();
        String str = okNameForIsGetter(am, name, stdNaming);
        if (str == null) {
            str = okNameForRegularGetter(am, name, stdNaming);
        }
        return str;
    }
    
    /**
     * @since 2.5
     *
     * @deprecated Since 2.12 replaced with {@link com.fasterxml.jackson.databind.introspect.AccessorNamingStrategy}
     */
    @Deprecated
    public static String okNameForRegularGetter(AnnotatedMethod am, String name,
            boolean stdNaming)
    {
        if (name.startsWith("get")) {
            /* 16-Feb-2009, tatu: To handle [JACKSON-53], need to block
             *   CGLib-provided method "getCallbacks". Not sure of exact
             *   safe criteria to get decent coverage without false matches;
             *   but for now let's assume there's no reason to use any 
             *   such getter from CGLib.
             *   But let's try this approach...
             */
            if ("getCallbacks".equals(name)) {
                if (isCglibGetCallbacks(am)) {
                    return null;
                }
            } else if ("getMetaClass".equals(name)) {
                // 30-Apr-2009, tatu: Need to suppress serialization of a cyclic reference
                if (isGroovyMetaClassGetter(am)) {
                    return null;
                }
            }
            return stdNaming
                    ? stdManglePropertyName(name, 3)
                    : legacyManglePropertyName(name, 3);
        }
        return null;
    }

    /**
     * @since 2.5
     *
     * @deprecated Since 2.12 replaced with {@link com.fasterxml.jackson.databind.introspect.AccessorNamingStrategy}
     */
    @Deprecated
    public static String okNameForIsGetter(AnnotatedMethod am, String name,
            boolean stdNaming)
    {
        if (name.startsWith("is")) { // plus, must return a boolean
            Class<?> rt = am.getRawType();
            if (rt == Boolean.class || rt == Boolean.TYPE) {
                return stdNaming
                        ? stdManglePropertyName(name, 2)
                        : legacyManglePropertyName(name, 2);
            }
        }
        return null;
    }

    // since 2.9, not used any more by databind itself but somehow seems as if
    // it may have been used by JAXB module during 2.11
    @Deprecated
    public static String okNameForSetter(AnnotatedMethod am, boolean stdNaming) {
        return okNameForMutator(am, "set", stdNaming);
    }

    /**
     * @since 2.5
     *
     * @deprecated Since 2.12 replaced with {@link com.fasterxml.jackson.databind.introspect.AccessorNamingStrategy}
     */
    @Deprecated
    public static String okNameForMutator(AnnotatedMethod am, String prefix,
            boolean stdNaming) {
        String name = am.getName();
        if (name.startsWith(prefix)) {
            return stdNaming
                    ? stdManglePropertyName(name, prefix.length())
                    : legacyManglePropertyName(name, prefix.length());
        }
        return null;
    }

    /*
    /**********************************************************
    /* Value defaulting helpers
    /**********************************************************
     */
    
    /**
     * Accessor used to find out "default value" to use for comparing values to
     * serialize, to determine whether to exclude value from serialization with
     * inclusion type of {@link com.fasterxml.jackson.annotation.JsonInclude.Include#NON_DEFAULT}.
     *<p>
     * Default logic is such that for primitives and wrapper types for primitives, expected
     * defaults (0 for `int` and `java.lang.Integer`) are returned; for Strings, empty String,
     * and for structured (Maps, Collections, arrays) and reference types, criteria
     * {@link com.fasterxml.jackson.annotation.JsonInclude.Include#NON_DEFAULT}
     * is used.
     *
     * @since 2.7
     */
    public static Object getDefaultValue(JavaType type)
    {
        // 06-Nov-2015, tatu: Returning null is fine for Object types; but need special
        //   handling for primitives since they are never passed as nulls.
        Class<?> cls = type.getRawClass();

        // 30-Sep-2016, tatu: Also works for Wrappers, so both `Integer.TYPE` and `Integer.class`
        //    would return `Integer.TYPE`
        Class<?> prim = ClassUtil.primitiveType(cls);
        if (prim != null) {
            return ClassUtil.defaultValue(prim);
        }
        if (type.isContainerType() || type.isReferenceType()) {
            return JsonInclude.Include.NON_EMPTY;
        }
        if (cls == String.class) {
            return "";
        }
        // 09-Mar-2016, tatu: Not sure how far this path we want to go but for now
        //   let's add `java.util.Date` and `java.util.Calendar`, as per [databind#1550]
        if (type.isTypeOrSubTypeOf(Date.class)) {
            return new Date(0L);
        }
        if (type.isTypeOrSubTypeOf(Calendar.class)) {
            Calendar c = new GregorianCalendar();
            c.setTimeInMillis(0L);
            return c;
        }
        return null;
    }

    /*
    /**********************************************************
    /* Special case handling
    /**********************************************************
     */

    /**
     * This method was added to address the need to weed out
     * CGLib-injected "getCallbacks" method. 
     * At this point caller has detected a potential getter method
     * with name "getCallbacks" and we need to determine if it is
     * indeed injectect by Cglib. We do this by verifying that the
     * result type is "net.sf.cglib.proxy.Callback[]"
     */
    protected static boolean isCglibGetCallbacks(AnnotatedMethod am)
    {
        Class<?> rt = am.getRawType();
        // Ok, first: must return an array type
        if (rt.isArray()) {
            // And that type needs to be "net.sf.cglib.proxy.Callback".
            // Theoretically could just be a type that implements it, but
            // for now let's keep things simple, fix if need be.
            Class<?> compType = rt.getComponentType();
            // Actually, let's just verify it's a "net.sf.cglib.*" class/interface
            final String className = compType.getName();
            if (className.contains(".cglib")) {
                return className.startsWith("net.sf.cglib")
                    // also, as per [JACKSON-177]
                    || className.startsWith("org.hibernate.repackage.cglib")
                    // and [core#674]
                    || className.startsWith("org.springframework.cglib");
            }
        }
        return false;
    }

    /**
     * Another helper method to deal with Groovy's problematic metadata accessors
     */
    protected static boolean isGroovyMetaClassGetter(AnnotatedMethod am) {
        return am.getRawType().getName().startsWith("groovy.lang");
    }

    /*
    /**********************************************************
    /* Actual name mangling methods
    /**********************************************************
     */

    /**
     * Method called to figure out name of the property, given 
     * corresponding suggested name based on a method or field name.
     *
     * @param basename Name of accessor/mutator method, not including prefix
     *  ("get"/"is"/"set")
     */
    protected static String legacyManglePropertyName(final String basename, final int offset)
    {
        final int end = basename.length();
        if (end == offset) { // empty name, nope
            return null;
        }
        // next check: is the first character upper case? If not, return as is
        char c = basename.charAt(offset);
        char d = Character.toLowerCase(c);
        
        if (c == d) {
            return basename.substring(offset);
        }
        // otherwise, lower case initial chars. Common case first, just one char
        StringBuilder sb = new StringBuilder(end - offset);
        sb.append(d);
        int i = offset+1;
        for (; i < end; ++i) {
            c = basename.charAt(i);
            d = Character.toLowerCase(c);
            if (c == d) {
                sb.append(basename, i, end);
                break;
            }
            sb.append(d);
        }
        return sb.toString();
    }

    /**
     * Note: public only since 2.11
     *
     * @since 2.5
     */
    public static String stdManglePropertyName(final String basename, final int offset)
    {
        final int end = basename.length();
        if (end == offset) { // empty name, nope
            return null;
        }
        // first: if it doesn't start with capital, return as-is
        char c0 = basename.charAt(offset);
        char c1 = Character.toLowerCase(c0);
        if (c0 == c1) {
            return basename.substring(offset);
        }
        // 17-Dec-2014, tatu: As per [databind#653], need to follow more
        //   closely Java Beans spec; specifically, if two first are upper-case,
        //   then no lower-casing should be done.
        if ((offset + 1) < end) {
            if (Character.isUpperCase(basename.charAt(offset+1))) {
                return basename.substring(offset);
            }
        }
        StringBuilder sb = new StringBuilder(end - offset);
        sb.append(c1);
        sb.append(basename, offset+1, end);
        return sb.toString();
    }

    /*
    /**********************************************************
    /* Package-specific type detection for error handling
    /**********************************************************
     */

    /**
     * Helper method called by {@link com.fasterxml.jackson.databind.deser.BeanDeserializerFactory}
     * and {@link com.fasterxml.jackson.databind.ser.BeanSerializerFactory} to check
     * if given unrecognized type (to be (de)serialized as general POJO) is one of
     * "well-known" types for which there would be a datatype module; and if so,
     * return appropriate failure message to give to caller.
     *
     * @since 2.12
     */
    public static String checkUnsupportedType(JavaType type) {
        final String className = type.getRawClass().getName();
        String typeName, moduleName;

        if (isJava8TimeClass(className)) {
            // [modules-java8#207]: do NOT check/block helper types in sub-packages,
            // but only main-level types (to avoid issues with module)
            if (className.indexOf('.', 10) >= 0) {
                return null;
            }
            typeName =  "Java 8 date/time";
            moduleName = "com.fasterxml.jackson.datatype:jackson-datatype-jsr310";
        } else if (isJodaTimeClass(className)) {
            typeName =  "Joda date/time";
            moduleName = "com.fasterxml.jackson.datatype:jackson-datatype-joda";
        } else {
            return null;
        }
        return String.format("%s type %s not supported by default: add Module \"%s\" to enable handling",
                typeName, ClassUtil.getTypeDescription(type), moduleName);
    }

    /**
     * @since 2.12
     */
    public static boolean isJava8TimeClass(Class<?> rawType) {
        return isJava8TimeClass(rawType.getName());
    }

    private static boolean isJava8TimeClass(String className) {
        return className.startsWith("java.time.");
    }

    /**
     * @since 2.12
     */
    public static boolean isJodaTimeClass(Class<?> rawType) {
        return isJodaTimeClass(rawType.getName());
    }

    private static boolean isJodaTimeClass(String className) {
        return className.startsWith("org.joda.time.");
    }
}

⏎ com/fasterxml/jackson/databind/util/BeanUtil.java

Or download all of them as a single archive file:

File name: jackson-databind-2.14.0-sources.jar
File size: 1187952 bytes
Release date: 2022-11-05
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